Storage systems

NAS – Network Attached Storage

• NAS is basically a file server
• In case of traditional file servers, we have to use  separate file servers for Windows domain and Linux domain
• A NAS device can be used with Windows as well as Linux at the same time
• It can be accessed through network shares (eg : \\servername\sharename) or by mapping it as a network drive
• NFS, CIFS etc are the protocols mainly used in a NAS device
• NFS supports Linux/ Unix file shares
• CIFS supports Windows file shares
• Both NFS and CIFS are client-server protocols
• CIFS works on top of TCP/ IP
• NFS is based on Remote Procedure Calls (RPC)
• A redundant NAS solution can be created by clustering

SAN – Storage Area Network

Types of SAN

• FC SAN (Fiber Channel SAN)

• P2P connectivity
• FC-SW connectivity

• IP SAN

• iSCSI

• Software iSCSI
• Hardware iSCSI HBA

• FCIP

• FCOE SAN (Fiber Channel Over Ethernet SAN)

The main difference between SAN and NAS is that, using a SAN you can attach additional disk drives to a storage client machine from the storage server, which will appear as a local storage in the client machine. And the client can format the additional disk drive based on any file system supported by that machine. But in a NAS, the client machines can only access the files in the shared storage volume. Now we have “Unified storage” solutions offering both file level protocols (NAS) and block level protocols (SAN) from the same system. Highly available (HA) storage systems can be implemented by clustering multiple storage devices.

Examples for Unified storage solutions : FreeNAS 9.3, Open-E DSS V7, Openfiler etc.